Modern seagoing vessels, such as cargo, passenger, and war ships, have service requirements such as supply of electricity, cooling andor heating, fresh water supply, and waste management. In the Arleigh Burke class of destroyers, for example, all of these requirements are present. Electrical generation in an electric-drive vessel is often provided by large engine-driven generators which supply the propeller motors, and a portion of the generated power is tapped from the generators for ancillary or auxiliary purposes, such as "hotel" services. Hotel services includes such services as space heating andor cooling, lighting, and fresh water supply. Such a system requires an extensive power distribution system providing adequate power throughout the ship.
Air conditioning and heating services in ships are often provided by one or more heat exchangers or chillers which reject heat from chilled fresh water to sea water pumped from outside the ship. The chilled water is then distributed to points of use, which desirably should be near the heat exchanger to avoid excessive fluid runs and the associated efficiency losses. These requirements are often met by a few air conditioning systems spaced about the ship. Such air conditioning units may be very large. In the above-mentioned Arleigh Burke class ships, four such units are used, each of about 200 tons (2.5 million BTU) capacity. These units are spaced about the ship in locations central to regions of use.
Fresh water for ships is now provided by reverse-osmosis filtration or by boilers, both of which are often large centralized units, requiring distribution systems for the fresh water. Similarly, waste management regulation no longer permits overboard discharge of untreated waste.
Improved service systems are desired.